IDO1 and neoplasm: Patients exhibiting high IDO1 expression levels demonstrated significantly worse PFS and OS (***<i>P</i> < 0.001 and **<i>P</i> = 0.003, respectively).<h4>Conclusion</h4>High IDO1 expression in lung adenocarcinoma correlates with increased tumor invasiveness, metastatic potential, advanced clinical stage, and poorer prognosis.